The goal of this Mentored Research Scientist Development Award is to allow the applicant to develop the basic science and clinical research skills needed to pursue an independent, productive career in rehabilitation research. The applicant is a licensed physical therapist with doctoral and postdoctoral training in the neural control of movement. This award will enhance the applicant's ability to investigate mechanisms underlying loss and recovery of upper extremity function in people with stroke by combining the applicant's existing expertise in studying motor control with additional training in 1) the basic science and measurement of somatosensation, and 2) the design, statistical analyses, and execution of longitudinal clinical studies involving heterogeneous patient populations. The long-term objective is to develop an impairment-based model of upper extremity function that can be used to guide rehabilitation evaluation and treatment of people post stroke. The specific aims of the proposed studies are designed to test the general hypothesis that loss of hand function after stroke is due to loss of motor control and to loss of somatosensation. The proposed studies will investigate: 1) whether or not impairments in isolated motor control at segments proximal to the hand (i.e. the inability to position the hand in space) contribute to reduced hand function, 2) the extent to which impairments after stroke in elementary and intermediate somatosensory modalities recover with time, and 3) whether or not impairments in somatosensation contribute to reduced hand function in people post stroke. To test these hypotheses, longitudinal kinematic measures of isolated motor control of all the segments of the upper extremity, detailed measures of elementary and intermediate somatosensory modalities in the upper extremity, and clinical measures of upper extremity function will be taken in people with pure motor hemiparesis, people with pure hemianesthesia, and people with hemiparesis plus hemianesthesia. Multiple regression techniques will be used to determine how impairments in motor control at the different segments and impairments in the different somatosensory modalities contribute to loss of hand function. Results of the proposed studies will provide insight into how impairments post stroke contribute to disability of the upper extremity and will be useful for rehabilitation professionals during the evaluation and treatment of people with stroke.